JP2009084494A - Aqueous colorant dispersion, method of producing aqueous colorant dispersion, and aqueous ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous colorant dispersion in which a colorant is finely dispersed and which is excellent in temporal stability, a method of producing the dispersion, and an aqueous ink for inkjet recording comprising the dispersion. <P>SOLUTION: The aqueous colorant dispersion comprises the colorant (A), a polymer (B) and an aqueous liquid medium (I), wherein the polymer (B) is a copolymer containing >80 to <100 mass% of a hydrophobic structural unit and a hydrophilic structural unit. The polymer contains a hydrophobic structural unit (a) containing a benzene ring which is not directly bonded to an atom that forms a main chain of the polymer (B) as the above hydrophobic structural unit and a hydrophilic structural unit (b) containing an ionic group as the above hydrophilic structural unit. The polymer (B) contains >15 to <90 mass% of a structural unit (c) different from the hydrophobic structural unit (a) and the hydrophilic structural unit (b). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aqueous colorant dispersion excellent in colorant dispersibility, a method for producing an aqueous colorant dispersion, and an aqueous ink for inkjet recording.

  In recent years, paints and inks (hereinafter also referred to as “inks”) are becoming water-based due to increasing needs such as resource protection, environmental protection, and improvement of work stability. The quality required for water-based paints and water-based inks is fluidity, storage stability, gloss of film, vividness, coloring power and the like, similar to oil-based paints and oil-based inks. However, since most pigments are remarkably inferior in suitability for pigment dispersibility and the like as compared with an oily vehicle with respect to an aqueous vehicle, satisfactory quality cannot be obtained by a normal dispersion method. Therefore, the use of various additives such as aqueous pigment dispersion resins and surfactants has been studied so far, but they satisfy all the above-mentioned suitability and are comparable to existing high-quality oil-based paints or oil-based inks. No water-based paint or water-based ink has been obtained.

In order to solve such a problem, for example, a monomer containing a pigment, a dispersant, a water-soluble organic solvent, and water, the dispersant having a hydrophilic portion and a hydrophobic portion, and constituting the hydrophilic portion An aqueous pigment ink containing 3 to 25 mol% of a long-chain nonionic group-containing monomer having a phenyl group at the terminal and 5 to 60 mol% of an α, β-ethylenically unsaturated carboxylic acid is disclosed (for example, (See Patent Document 1).
Further, an aqueous pigment dispersion for preparing an aqueous pigment ink for ink-jet recording, which comprises an organic pigment, an acrylic copolymer (A), a basic substance, and water, and an acrylic copolymer that does not cover the organic pigment. In the aqueous pigment dispersion-containing composition for preparing an aqueous pigment ink for ink-jet recording containing the polymer (B), the acrylic copolymer (A) contains (meth) acrylic containing a benzene ring on a mass basis. The total of the acid ester monomer and the (meth) acrylic acid monomer is an acrylic copolymer having 85% or more of the total polymerization units, an acid value of 40 to 100 mgKOH / g, and a hydroxyl value of 10 mgKOH / g or less, The acrylic copolymer (B) has a (meth) acrylic acid ester monomer containing a benzene ring and a (meth) acrylic acid monomer as essential components, and has an acid value of 40 to 100 mgKO. / G acrylic copolymer aqueous pigment dispersion-containing composition for ink jet recording water-based pigment ink prepared is (B) has been disclosed (e.g., see Patent Document 2.).
Japanese Patent No. 3444920 JP 2007-511199 A

However, in Patent Document 1, a long-chain nonion group-containing monomer having a phenyl group at the terminal is regarded as a hydrophilic portion, and the amount contained in the polymer is not sufficient, and as a result, the technique disclosed herein is applied. In the dispersant synthesized in this manner, the dispersibility of the colorant is insufficient, and in Patent Document 2, the dispersed particle diameter of the colorant cannot be made sufficiently small, and the performance as an aqueous colorant dispersion is sufficient. It was not satisfactory.
An object of the present invention is to solve the above conventional problems and achieve the following objects.
That is, an object of the present invention is to provide a water-based colorant dispersion in which a colorant is finely dispersed and excellent in stability over time, and a method for producing the water-based colorant dispersion.
Another object of the present invention is to provide a water-based ink for inkjet recording containing the water-based colorant dispersion.

<1> A water-based colorant dispersion containing a colorant (A), a polymer (B), and an aqueous liquid medium (I), wherein the polymer (B) exceeds 100% by mass with the hydrophilic structural unit. A copolymer containing less than% hydrophobic structural units,
The hydrophobic structural unit includes a hydrophobic structural unit (a) containing a benzene ring that is not directly bonded to an atom forming the main chain of the polymer (B),
A structural unit (c) containing a hydrophilic structural unit (b) containing an ionic group as the hydrophilic structural unit and different from the hydrophobic structural unit (a) and the hydrophilic structural unit (b) An aqueous colorant dispersion characterized by containing more than 15% by weight and less than 90% by weight.

<2> The aqueous colorant dispersion as described in <1> above, wherein the hydrophobic structural unit (a) has a structure represented by the following general formula (1).

(In the formula, * represents a connection point with the main chain, and L represents a divalent linking group having 1 to 30 carbon atoms.)

<3> The aqueous colorant dispersion according to <1> or <2>, wherein the hydrophobic structural unit (a) includes a structural unit represented by the following general formula (2).

(Wherein, _{R 1} represents a hydrogen atom, a methyl group or a halogen _atom,, L 1 is -COO -, - OCO -, - CONH -, - represents O-, or a substituted or unsubstituted phenylene group, _{L 2} Represents a single bond or a divalent linking group having 1 to 30 carbon atoms.)

<4> The aqueous colorant dispersion described in any one of <1> to <3>, wherein the hydrophobic structural unit (a) includes a structural unit derived from benzyl acrylate or benzyl methacrylate. .
<5> The aqueous colorant dispersion described in any one of <1> to <4> above, wherein the ionic group of the hydrophilic structural unit (b) is an anionic group.

<6> The aqueous coloring according to any one of <1> to <5>, wherein the anionic group is at least one selected from a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Agent dispersion.
<7> The water-based colorant dispersion according to any one of <1> to <6>, wherein the hydrophilic structural unit (b) includes a structural unit derived from acrylic acid or methacrylic acid. object.
<8> The aqueous colorant dispersion described in any one of <1> to <7>, wherein the acid value of the polymer (B) is 10 mgKOH / g or more and less than 85 mgKOH / g.

<9> Any of the above <1> to <8>, wherein the structural unit (c) includes a hydrophobic structural unit derived from an alkyl ester having 1 to 6 carbon atoms of acrylic acid or methacrylic acid. The aqueous colorant dispersion according to claim 1.
<10> The aqueous colorant dispersion described in any one of <1> to <9> above, wherein the structural unit (c) includes a hydrophilic structural unit having an alkylene oxide polymer structure. .

<11> The aqueous colorant dispersion described in any one of <1> to <10>, wherein the structural unit (c) includes a hydrophilic structural unit having a hydroxyl group.
<12> The aqueous colorant dispersion described in any one of the above items <1> to <11>, wherein the colorant (A) is a pigment.

<13> A mixture (II) of a colorant (A), a polymer (B), and an organic solvent (C) that dissolves the polymer (B) and is substantially incompatible with water contains a basic substance and mainly contains water. The method for producing an aqueous colorant dispersion according to any one of <1> to <12>, wherein the organic solvent (C) is removed after adding the solution (III) as a component.
<14> A water-based ink for ink-jet recording comprising the water-based colorant dispersion described in any one of the above items <1> to <12>.

According to the present invention, it is possible to provide an aqueous colorant dispersion in which a colorant is finely dispersed and excellent in stability over time, and a method for producing the aqueous colorant dispersion.
Moreover, according to this invention, the aqueous ink for inkjet recording containing the said aqueous coloring agent dispersion can be provided.

Details of the present invention will be described below.
The aqueous colorant dispersion of the present invention is an aqueous colorant dispersion containing a colorant (A), a polymer (B), and an aqueous liquid medium (I), wherein the polymer (B) is a hydrophilic structural unit. It is a copolymer containing more than 80% by weight and less than 100% by weight of hydrophobic structural units, and is not directly bonded to the atoms forming the main chain of the polymer (B) as the hydrophobic structural units. A hydrophobic structural unit (a) containing a benzene ring, the hydrophilic structural unit containing a hydrophilic structural unit (b) containing an ionic group, and the hydrophobic structural unit (a) and the above More than 15 mass% and less than 90 mass% of structural units (c) different from a hydrophilic structural unit (b) are contained, It is characterized by the above-mentioned.
When the water-based colorant dispersion of the present invention has the above-described configuration, the colorant is finely dispersed and becomes a dispersion excellent in stability over time.

(Colorant (A))
The colorant (A) in the present invention will be described in detail.
As the colorant in the present invention, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a colorant that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes that form J aggregates, and more preferably pigments from the viewpoint of light resistance.

  There is no restriction | limiting in particular as a pigment in this invention, A conventionally well-known organic and inorganic pigment can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthaloni pigments, basic Examples include dye lakes such as dye-type lakes and acid dye-type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. Any pigment not described in the color index can be used as long as it can be dispersed in the aqueous phase. Further, it is of course possible to use a pigment obtained by surface-treating the above pigment with a surfactant, a polymer dispersing agent or the like, or graft carbon. Of the above pigments, organic pigments and carbon black pigments are particularly preferably used from the viewpoint of ink colorability.

Specific examples of the organic pigment used in the present invention are shown below.
Examples of organic pigments for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of organic pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 222C. I. Pigment violet 19 and the like.

Examples of organic pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and siloxane-crosslinked aluminum phthalocyanine described in U.S. Pat. No. 4,311,775.
Examples of organic pigments for black include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.
The colorants may be used alone or in combination.

  The content of the colorant in the aqueous colorant dispersion is preferably 0.1 to 20% by mass with respect to the total solid mass of the dispersion, from the viewpoint of ink colorability, storage stability, and the like. 2 to 15% by mass is more preferable, and 0.5 to 10% by mass is particularly preferable.

[Polymer (B)]
The polymer (B) in the present invention will be described in detail.
The polymer (B) is used as a dispersant for the colorant (A) in the aqueous liquid medium (I).
The structure of the polymer (B) is composed of a hydrophobic structural unit and a hydrophilic structural unit.
The composition of the hydrophilic structural unit and the hydrophobic structural unit depends on the degree of hydrophilicity and hydrophobicity, but the hydrophobic structural unit exceeds 80% by mass with respect to the total mass of the polymer (B). It is necessary to contain, 85 mass% or more is more preferable, and 90 mass% or more is especially preferable. That is, the hydrophilic structural unit needs to be 20% by mass or less, and when there are more hydrophilic structural units than this, it does not contribute to the dispersion of the colorant and dissolves alone in the water-soluble medium (I). Ingredients increase and cause various performances such as dispersibility of the colorant (A).

<Hydrophobic structural unit>
(Structural unit (a) containing a benzene ring not directly bonded to the atoms forming the main chain)
The polymer (B) of the present invention comprises a hydrophobic structural unit (a) containing a benzene ring that is not directly bonded to the atoms forming the main chain of the polymer (B) (hereinafter simply referred to as “ At least a hydrophobic structural unit (a) ".
Here, “not directly bonded” means that the benzene ring and the atoms forming the main chain structure of the polymer have a structure bonded via a linking group. By having such a form, an appropriate distance is maintained between the hydrophilic structural unit in the polymer (B) and the hydrophobic benzene ring, so that the polymer (B) and the colorant (A) Interactions are likely to occur, and they are strongly adsorbed, resulting in improved dispersibility.

  The hydrophobic structural unit (a) having a benzene ring that is not directly bonded to the atoms forming the main chain of the polymer (B) is 30% by mass or more and less than 83% by mass of the total mass of the polymer (B). It is preferable that it is 45 mass% or more and less than 83 mass%, and it is especially preferable that it is 58 mass% or more and less than 75 mass%.

  In the present invention, the benzene ring in the hydrophobic structural unit (a) is preferably introduced into the polymer (B) with a structure represented by the following general formula (1).

  In general formula (1), * represents a connection point with the main chain of the polymer (B), L represents a divalent linking group having 1 to 30 carbon atoms, more preferably a connection having 1 to 25 carbon atoms. And particularly preferably a linking group having 1 to 20 carbon atoms. The divalent linking group may be saturated or unsaturated, may have a linear structure, a branched structure, or a ring structure, and may contain a heteroatom selected from O, N, and S. good.

  As the hydrophobic structural unit (a) containing a benzene ring that is not directly bonded to atoms forming the main chain of the polymer (B), a particularly preferred example of the general formula (1) is the following general formula. The structure represented by (2) can be mentioned.

In General Formula (2), R ₁ represents a hydrogen atom, a methyl group, or a halogen atom, L ₁ represents —COO—, —OCO—, —CONR ₂ —, or a substituted or unsubstituted phenylene group; ₂ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. L ₂ represents a single bond or a divalent linking group having 1 to 29 carbon atoms, and when it is a divalent linking group, its preferred range is the same as L. Here, examples of the substitution include a halogen atom, an alkyl group, an alkoxy group, a hydroxyl group, and a cyano group, but are not particularly limited.

Among the general formula (2), a combination of structural units in which R ₁ is a hydrogen atom or a methyl group, L ₁ is —COO—, and L ₂ has 1 to 4 carbon atoms is preferable, and more preferably , R ₁ is a hydrogen atom or a methyl group, L ₁ is —COO—, and L ₂ is a combination of structural units each having a C 1 divalent linking group. Corresponding monomers are benzyl acrylate or benzyl methacrylate.

<Hydrophilic structural unit>
The hydrophilic structural unit constituting the polymer (B) in the present invention will be described.
The hydrophilic structural unit is contained in an amount of 2% by mass to 20% by mass with respect to the total mass of the polymer (B), preferably 2% by mass to 15% by mass, and more preferably 5% by mass to 12% by mass. More preferred.
The polymer (B) includes at least a hydrophilic structural unit (b) containing an ionic group as a hydrophilic structural unit (hereinafter also simply referred to as “hydrophilic structural unit (b)”).

(Hydrophilic structural unit (b) containing an ionic group)
The content of the hydrophilic structural unit (b) containing an ionic group needs to be changed depending on whether the structural unit (c) described later is hydrophilic, hydrophobic, or both.
That is, the polymer (B) in the present invention may contain an amount of more than 80% by mass as the hydrophobic structural unit and an amount that makes the hydrophilic structural unit 20% by mass or less, and the hydrophobic structural unit (a ), The hydrophilic structural unit (b) and the structural unit (c).
For example, when the polymer (B) is composed of only the hydrophobic structural unit (a), the hydrophilic structural unit (b), and the structural unit (c), the ionicity is obtained when the structural unit (c) is hydrophilic. The content of the hydrophilic structural unit (b) containing a group can be determined by “(total mass% of hydrophilic structural unit) − (mass% of structural unit (c))”.
When the structural unit (c) is hydrophobic, the content of the hydrophilic structural unit (b) containing an ionic group is “100- (mass% of the hydrophobic structural unit (a)) − (structural unit). (% By mass of (c)) ”.

The structural unit (b) containing an ionic group can be obtained by polymerizing an ionic group-containing monomer. After polymerizing a polymer having no ionic group, an ionic group (anion) is added to the polymer chain. Or a cationic group) may be introduced.
Examples of the ionic group include an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as an amino group and an ammonium group. Among these, a carboxyl group, a sulfonic acid group, and a phosphoric acid group are selected. One or more anionic groups are preferred.
Examples of the anionic group-containing monomer and the cationic group-containing monomer that can be used in the present invention are listed below, but are not limited thereto.

  Among the anionic group-containing monomers, those containing a carboxyl group include, for example, unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and β- Examples thereof include carboxyethyl acrylic acid and 2-methacryloyloxymethyl succinic acid. Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned. Examples of the phosphoric acid group-containing monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl. A phosphate etc. are mentioned.

Examples of the cationic group-containing monomer include one or more selected from the group consisting of tertiary amine-containing vinyl monomers and ammonium salt-containing vinyl monomers.
Examples of the tertiary amine-containing vinyl monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N- Examples include dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine, and the like.
Examples of the ammonium salt-containing monomer include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, and N, N-dimethylaminopropyl (meth) acrylate quaternized product. And the like.

Among these, anionic monomers are preferable, and unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are particularly preferable from the viewpoints of ink viscosity and dischargeability. In addition, an ionic group containing monomer can be used individually or in mixture of 2 or more types.

When the polymer (B) of the present invention contains an acidic group such as carboxylic acid, the acid value of the polymer (B) is preferably 10 mgKOH / g or more and less than 85 mgKOH / g, 15 mgKOH / g or more, 85 mgKOH / g Is more preferably 15 mgKOH / g or more and less than 80 mgKOH / g. The acid value here is defined by the mass (mg) of KOH required to completely neutralize 1 g of the polymer (B), and the method described in JIS standard (JIS K0070: 1992) was adopted.
When the acid value of the polymer (B) in the case of containing an acidic group such as carboxylic acid is less than 10 mgKOH / g, the charge repulsion of the dispersion due to the dissociated carboxyl group is insufficient, resulting in a decrease in dispersibility. In addition, when the concentration is 85 mgKOH / g or more, the hydrophilicity of the polymer becomes high, and the polymer tends not to be adsorbed to the colorant and to be eluted in the aqueous medium.

<Structural unit (c)>
The polymer (B) in the present invention comprises a structural unit (c) having a structure different from the structural unit (a) and the structural unit (b) (hereinafter also simply referred to as “structural unit (c)”). Contains at least.
The structural unit (c) different from the hydrophobic structural unit (a) and the hydrophilic structural unit (b) is a structural unit (c) having a structure different from the above (a) or (b). The structural unit (c) may be a hydrophobic structural unit or a hydrophilic structural unit.

By having the structural unit (c) in the polymer (B), the aqueous colorant dispersion of the present invention exhibits good dispersibility. The mechanism is unknown in detail, but is speculated as follows.
That is, the polymer (B) has a so-called contradictory property, that is, a hydrophobic structural unit (a) mainly having an affinity for a colorant and a hydrophilic structural unit (b) mainly having an affinity for an aqueous medium. Includes structural units. If the polymer (B) is formed only of these, each of the hydrophobic structural unit (a) and the hydrophilic structural unit (b) inhibits the function of each other, resulting in insufficient dispersibility. End up. When the polymer (B) contains the structural unit (c) showing intermediate properties between the hydrophobic structural unit (a) and the hydrophilic structural unit (b), such a problem is solved, and the present invention It is thought that the good dispersibility of is shown.

The structural unit (c) may be a hydrophilic structural unit or a hydrophobic structural unit. What are the hydrophilic structural unit (a) and the hydrophobic structural unit (b)? It needs to be a structural unit having a different structure.
The structural unit (c) is contained in the polymer (B) in an amount exceeding 15% by mass in the total mass, more preferably more than 15% by mass and 50% by mass or less, more than 15% by mass and 40% by mass. % Or less, more preferably 20% by mass or more and 30% by mass or less.

When the structural unit (c) is a hydrophobic structural unit, the structural unit (c) can be formed by polymerizing a monomer corresponding to the structural unit (c). Moreover, you may introduce | transduce a hydrophobic functional group into a polymer chain after superposition | polymerization of a polymer.
The monomer in the case where the structural unit (c) is a hydrophobic structural unit is not particularly limited as long as it has a functional group capable of forming a polymer and a hydrophobic functional group, and any known monomers Can also be used.
Examples of the monomer capable of forming the hydrophobic structural unit include vinyl monomers ((meth) acrylates, (meth) acrylamides, styrenes, vinyl esters, etc.) from the viewpoints of availability, handleability, and versatility. Is preferred.
Examples of these include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl ( Examples include alkyl (meth) acrylates such as (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, and (iso) stearyl (meth) acrylate. ) Acrylate is preferred.

  Examples of (meth) acrylamides include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and Nn-butylacryl (meth) amide. N-t-butyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide, N- (2-methoxyethyl) (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) Examples include (meth) acrylamides such as acrylamide, vinyl (meth) acrylamide, N, N-diallyl (meth) acrylamide, and N-allyl (meth) acrylamide. Among them, (meth) acrylamide, N, N-dimethyl (meta) ) Acrylamide is preferred.

  Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, n-butyl styrene, tert-butyl styrene, methoxy styrene, butoxy styrene, acetoxy styrene, chlorostyrene, dichlorostyrene, bromostyrene, Examples include chloromethylstyrene, hydroxystyrene protected with a group that can be deprotected by an acidic substance (for example, t-Boc, etc.), methyl vinylbenzoate, α-methylstyrene, vinylnaphthalene, and the like. Styrene is preferred.

Examples of the vinyl esters include vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl methoxyacetate, and vinyl benzoate. Of these, vinyl acetate is preferable.
These can be used alone or in admixture of two or more.

When the structural unit (c) is a hydrophilic structural unit, the structural unit (c) preferably contains a nonionic hydrophilic group. The structural unit (c) can be formed by polymerizing a monomer corresponding to the structural unit (c), but a hydrophilic functional group may be introduced into the polymer chain after the polymerization of the polymer.
The monomer for forming the structural unit (c) is not particularly limited as long as it has a functional group capable of forming a polymer and a nonionic hydrophilic functional group, and any known monomer is used. However, vinyl monomers are preferred from the viewpoints of availability, handleability, and versatility.
Examples of these vinyl monomers include (meth) acrylates, (meth) acrylamides, and vinyl esters having a hydrophilic functional group. Examples of the hydrophilic functional group include a hydroxyl group, an amide group (the nitrogen atom is unsubstituted), and alkylene oxide polymers such as polyethylene oxide and polypropylene oxide as described later. Of these, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylamide, and (meth) acrylate containing an alkylene oxide polymer are particularly preferable.

The structural unit (c) preferably includes a hydrophilic structural unit having an alkylene oxide polymer structure.
The alkylene of the alkylene oxide polymer preferably has 1 to 6 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms from the viewpoint of hydrophilicity / hydrophobicity.
Moreover, as a polymerization degree of the said alkylene oxide polymer, 1-120 are preferable, 1-60 are more preferable, and 1-30 are especially preferable.

It is also a preferred embodiment that the structural unit (c) is a hydrophilic structural unit containing a hydroxyl group.
The number of hydroxyl groups in the structural unit (c) is not particularly limited, and is preferably 1 to 4 from the viewpoint of hydrophilicity / hydrophobicity of the polymer (B) and compatibility with the solvent and other monomers during polymerization. 3 is more preferable, and 1-2 is particularly preferable.

  The polymer (B) in the present invention may be a random copolymer in which each structural unit is irregularly introduced, or a block copolymer in which the structural units are regularly introduced. Each structural unit in a certain case may be synthesized in any order of introduction, and the same constituent component may be used twice or more, but a random copolymer is versatile and manufacturable. This is preferable.

Furthermore, the molecular weight range of the polymer (B) used by this invention is a weight average molecular weight (Mw), Preferably it is 1000-1 million, More preferably, it is 2000-200,000, More preferably, it is 3000-100,000. is there.
By setting the molecular weight within the above range, the steric repulsion effect as a dispersing agent tends to be good, and it is preferable from the viewpoint of the tendency that adsorption to the colorant does not take time due to the steric effect.
In addition, the molecular weight distribution (expressed by weight average molecular weight value / number average molecular weight value) of the polymer used in the present invention is preferably 1 to 6, and more preferably 1 to 4.
By setting the molecular weight distribution within the above range, it is preferable from the viewpoint of shortening the dispersion time of the pigment and stability with time of the dispersion. Here, the number average molecular weight and the weight average molecular weight are detected by a solvent THF and a differential refractometer using a GPC analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation). The molecular weight is expressed using polystyrene as a standard substance.

The polymer used in the present invention can be synthesized by various polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, precipitation polymerization, bulk polymerization, and emulsion polymerization. The polymerization reaction can be performed by a known operation such as a batch system, a semi-continuous system, or a continuous system.
The polymerization initiation method includes a method using a radical initiator, a method of irradiating light or radiation, and the like. These polymerization methods and polymerization initiation methods are, for example, the revised version of Tsuruta Junji “Polymer Synthesis Method” (published by Nikkan Kogyo Shimbun, 1971), Takatsu Otsu, Masato Kinoshita, “Experimental Methods for Polymer Synthesis” It is described in pp. 47-154 published in 1972.
Among the above polymerization methods, a solution polymerization method using a radical initiator is particularly preferable. Solvents used in the solution polymerization method include, for example, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, benzene, toluene, acetonitrile, A single organic solvent such as methylene chloride, chloroform, dichloroethane, methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol, or a mixture of two or more thereof may be used, or a mixed solvent with water may be used.
The polymerization temperature needs to be set in relation to the molecular weight of the polymer to be produced, the type of initiator, etc., and is usually about 0 ° C. to 100 ° C., but the polymerization is preferably carried out in the range of 50 to 100 ° C.
The reaction pressure can be appropriately selected, but is usually preferably 1 to 100 kg / cm ² , particularly preferably about 1 to 30 kg / cm ² . The reaction time is about 5 to 30 hours. The obtained polymer may be subjected to purification such as reprecipitation.

  Specific preferred examples of the polymer (B) in the present invention are shown below, but the present invention is not limited to the following.

(Aqueous liquid medium (I))
The aqueous liquid medium in the aqueous colorant dispersion of the present invention contains water, but can further contain a water-soluble organic solvent. The water-soluble organic solvent can be contained as a drying inhibitor and a penetration enhancer.
The anti-drying agent can effectively prevent nozzle clogging that may occur due to drying of ink at the ink ejection port, particularly when the aqueous ink composition of the present invention is applied to an image recording method using an ink jet method. .

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Specific examples of the drying inhibitor include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, Polyhydric alcohols represented by acetylene glycol derivatives, glycerin, trimethylolpropane, etc., polyvalent alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether Lower alkyl ethers of alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, dimethyls Sulfoxide, sulfur-containing compounds such as sulfolane, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives. Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred as the drying inhibitor. Moreover, said drying inhibitor may be used independently or may be used together 2 or more types. These drying inhibitors are preferably contained in the ink in an amount of 10 to 50% by mass.

  Further, the penetration accelerator is preferably used for the purpose of allowing the ink to penetrate better into the recording medium (printing paper). Specific examples of penetration enhancers include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonionic surfactants. Etc. can be used suitably. These penetration enhancers exhibit a sufficient effect when contained in the ink composition in an amount of 5 to 30% by mass. Further, it is preferable that the penetration enhancer is used within a range of an addition amount that does not cause printing bleeding and paper loss (print through).

In addition to the above, the water-soluble organic solvent can be used for adjusting the viscosity. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, Cyclohexanol, benzyl alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Ter, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, Tylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
In addition, a water-soluble organic solvent may be used independently and may use 2 or more types together.
The content of the aqueous liquid medium in the aqueous colorant dispersion of the present invention is preferably 1% by mass to 70% by mass from the viewpoint of liquid properties such as drying prevention, permeability to an adherend, and viscosity. 2 mass%-60 mass% are more preferable, and 5 mass%-50 mass% are especially preferable.
By setting the content of the aqueous liquid medium in the above range, the liquid properties such as the drying speed of the colorant dispersion, the permeability to the adherend, and the viscosity can be adjusted to an appropriate form.

In the aqueous colorant dispersion of the present invention, other additives can be added as necessary in addition to the essential components. As other additives, known pigment dispersions and additives that can be used in water-based inks can be used.
For example, anti-fading agent, emulsion stabilizer, penetration enhancer, ultraviolet absorber, preservative, antifungal agent, pH adjuster, surface tension adjuster, antifoaming agent, viscosity adjuster, dispersant, dispersion stabilizer, Well-known additives, such as a rust agent and a chelating agent, are mentioned. These various additives may be added during or after the preparation of the aqueous colorant dispersion.

(Other additives)
The ultraviolet absorber is used for the purpose of improving image storability. Examples of ultraviolet absorbers include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-211141, Cinnamic acid compounds described in, for example, Kaihei 10-88106, JP-A-4-298503, 8-53427, 8-239368, 10-182621, JP-A-8- No. 501291, etc., triazine compounds, Research Disclosure No. Compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based and benzoxazole-based compounds, so-called fluorescent brighteners, can also be used.

  The anti-fading agent is used for the purpose of improving image storage stability. As the antifading agent, various organic and metal complex antifading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like. More specifically, Research Disclosure No. No. 17643, No. VII, I to J, ibid. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds included in the general formulas and compound examples of typical compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the aqueous colorant dispersion in an amount of 0.02 to 1.00% by mass.
As the pH adjuster, basic substances (neutralizing agents such as organic bases and inorganic alkalis) can be used. For the purpose of improving the storage stability of the aqueous colorant dispersion, the basic substance is preferably added so that the aqueous colorant dispersion has a pH of 6 to 10, and added so as to have a pH of 7 to 10. More preferred.
As the basic substance, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and organic amines such as diethanolamine and triethanolamine can be used. If necessary, organic acids such as citric acid and tartaric acid, mineral acids such as hydrochloric acid and phosphoric acid, and the like can be used. Among these, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide are preferable from the viewpoint of ease of use.

Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.
Further, the addition amount of the surface tension adjusting agent is preferably an addition amount for adjusting the surface tension of the aqueous ink composition to 20 to 60 mN / m in order to drop the aqueous colorant dispersion as it is by the ink jet method. The addition amount adjusted to 20 to 45 mN / m is more preferable, and the addition amount adjusted to 20 to 40 mN / m is more preferable.
The surface tension of the aqueous colorant dispersion was measured using, for example, the Wilhelmy method.

Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.
Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
Also, fluorine (fluorinated alkyl) surfactants, silicone surfactants, and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are disclosed. By using, the abrasion resistance can be improved.
These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

The viscosity of the aqueous colorant dispersion is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, from the viewpoint of droplet ejection stability and agglomeration speed when ink is applied by an inkjet method. More preferably, the range of 2.5 to 15 mPa · s is particularly preferable. In addition, the value of a viscosity here shall be a measured value in 25 degreeC.
The viscosity of the water-based ink composition can be measured using, for example, an E-type viscometer.

(Method for producing aqueous colorant dispersion)
The method for producing an aqueous colorant dispersion of the present invention comprises a colorant (A), a polymer (B), an organic solvent (C) in which the polymer (B) is dissolved or dispersed, and a basic substance and water as a main component. After the solution (III) is mixed (mixing / hydration step), the organic solvent (C) is removed (solvent removal step).
According to the method for producing an aqueous colorant dispersion of the present invention, an aqueous colorant dispersion in which the colorant is finely dispersed and excellent in storage stability can be produced.

  The organic solvent (C) in the present invention needs to be able to dissolve or disperse the polymer (B) in the present invention. In addition to this, it is preferable that the organic solvent (C) has a certain affinity for water. Specifically, the solubility in water at 20 ° C. is preferably 10% by mass or more and 50% by mass or less.

  In more detail, the aqueous colorant dispersion of the present invention can be produced by a production method comprising steps (1) and (2) shown below, but is not limited thereto.

Step (1): Colorant (A), polymer (B), organic solvent (C) for dissolving / dispersing polymer (B), solution (III) containing a basic substance and containing water as a main component, and Step (2) of dispersing the mixture containing water: Step of removing the organic solvent (C) In the step (1), first, the polymer (B) is dissolved in the organic solvent (C), or Disperse to obtain a mixture (II) (mixing step). Next, a colorant (A), a solution (III) containing a basic substance and containing water as a main component, water, and a surfactant as necessary are added to the mixture (II) and mixed and dispersed. An oil-in-water type aqueous colorant dispersion is obtained.
There is no particular limitation on the degree of neutralization. Usually, it is preferable that the finally obtained aqueous colorant dispersion has neutral liquidity, for example, pH of 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the water-insoluble vinyl polymer.

  The colorant (A), polymer (B), and other additives used in the method for producing the aqueous colorant dispersion are the same as those described in the above-mentioned aqueous colorant dispersion, and preferred examples are also included. It is the same.

Preferable examples of the organic solvent (C) used in the present invention include alcohol solvents, ketone solvents, and ether solvents. Among these, examples of alcohol solvents include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, and diacetone alcohol. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable.
These organic solvents (C) may be used alone or in combination.

In the production of the water-based colorant dispersion, a strong shearing force is applied using a two-roll, three-roll, ball mill, tron mill, disper, kneader, kneader, homogenizer, blender, single-screw or twin-screw extruder, etc. The kneading and dispersing process can be performed while feeding.
For details on kneading and dispersing, see T.W. C. “Paint Flow and Pigment Dispersion” by Patton (published by John Wiley and Sons, 1964) and the like.
If necessary, use a vertical or horizontal sand grinder, pin mill, slit mill, ultrasonic disperser, etc. to finely disperse with beads made of glass with a particle diameter of 0.01 to 1 mm, zirconia, etc. Can be obtained.

  In the method for producing the aqueous colorant dispersion of the present invention, the removal of the organic solvent is not particularly limited, and can be removed by a known method such as vacuum distillation.

The average particle size of the colorant obtained by the method for producing the aqueous colorant dispersion of the present invention is preferably 10 nm or more and less than 200 nm, more preferably 50 nm or more and less than 130 nm, and further preferably 60 nm or more and less than 100 nm. By setting it as such a range, it is preferable at the point from which the color development property, dispersion stability, and the discharge stability at the time of jetting become favorable.
The average particle diameter of the dispersed particles of the colorant is a value measured using a dynamic light scattering method.

  The aqueous colorant dispersion of the present invention can be used, for example, in an aqueous ink for ink jet recording described later, and an aqueous ink for writing instruments such as an aqueous ballpoint pen and a marker pen. In this case, in order to prevent the inkjet nozzle and the nib from being clogged by drying, a low-volatile or non-volatile solvent can be added among the above water-soluble organic solvents. In order to increase the permeability to the recording medium, a volatile solvent can be added.

(Water-based ink for inkjet recording)
The water-based ink for ink-jet recording of the present invention (hereinafter referred to as “water-based ink” as appropriate) comprises the water-based colored dispersion of the present invention.
The water-based ink for ink-jet recording of the present invention is obtained by adding the water-based colorant dispersion of the present invention as it is or, if necessary, further adding the anti-drying agent or the other additives to the aqueous liquid medium (I ) And can be prepared.

  The amount of the colorant contained in the water-based ink is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.5 to 10% by mass, from the viewpoints of ink colorability, storage stability, and dischargeability. .

  The amount of the polymer (B) contained in the water-based ink is in the range of 1 to 150% by weight with respect to the pigment (colorant) from the viewpoint of dispersibility, storage stability, and dischargeability of the water-based ink. It is preferable that the range be 5 to 100% by mass.

The pH of the water-based ink is preferably in the range of 7-10. By setting the pH within this range, storage stability can be improved, and corrosion of members of an ink jet recording apparatus, which is an apparatus to which aqueous ink is applied, can also be suppressed.
The pH adjustment in the water-based ink can be prepared using the basic substance described in the section of the aqueous colorant dispersion.

  In order to prevent the ink jet nozzle from being clogged by drying, the water-based ink of the present invention may be added with a low-volatile or non-volatile solvent among the above water-soluble organic solvents. In order to increase the permeability to the recording medium, a volatile solvent may be added. It is also preferable to add a surfactant in order to give the ink an appropriate surface tension.

  The present invention will be described more specifically with reference to the following examples. The scope of the present invention is not limited to the specific examples shown below.

[Synthesis Example 1] (Synthesis of B-59)
Synthesized according to the following scheme.

To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 90 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.80 g of dimethyl 2,2′-azobisisobutyrate, 65 g of benzyl methacrylate, A solution in which 10 g of methacrylic acid, 5 g of methoxypolyethylene glycol monomethacrylate (Blenmer PME1000, manufactured by Nippon Oil & Fats Co., Ltd.) and 20 g of styrene were dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.8 g of dimethyl 2,2′-azobisisobutyrate dissolved in 10 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess of hexane, and the precipitated polymer was dried to obtain 96 g of B-59.
The composition of the obtained polymer was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 36000. Furthermore, when the acid value of this polymer was calculated | required by the method of JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

  Other polymers in the present invention can be synthesized in the same manner.

[Example 1: Preparation of pigment dispersion (D-1)]
A pigment dispersion was prepared by the following procedure using a Frichtux planetary ball mill model P-7 (manufactured by Fritsch).
B-59 obtained in Synthesis Example 1 was adjusted to a MEK solution having a solid content of 40% by mass. In a 45 ml container made of zirconia, 1.0 g of PB15: 3 pigment powder (phthalocyanine blue A220 manufactured by Dainichi Seika), 1.25 g of MEK solution of adjusted B-59, 3.75 g of MEK, 581 μL of 1N NaOH aqueous solution (dispersant) 1 equivalent) with respect to the amount of carboxylic acid contained in the container, and then add ultrapure water so that the total mass of the one in the container is 15 g, and then add 40 g of 0.1 mmΦ zirconia beads (TORAY Ray Treceram beads). And gently mixed with a spatula.

  A 45 ml container made of zirconia was placed in an overpot special atmosphere control container, purged with nitrogen, and dispersed at a rotation speed of 300 rpm for 3 hours. After the dispersion, the beads were removed by filtration with a filter cloth to obtain a pigment dispersion.

  Further, MEK is removed from the pigment dispersion by distillation under reduced pressure, and centrifuged at 5000 rpm for 30 minutes with a centrifuge (05P-21, manufactured by Hitachi, Ltd.), and then ion-exchanged water is added so that the pigment concentration becomes 15% by mass. The pigment dispersion was adjusted by addition. And after carrying out pressure filtration using a 2.5 micrometer membrane filter (made by Advantech), ion-exchange water is added so that it may become a pigment concentration of 4 mass%, and the pigment dispersion (D-1) of this invention Got.

[Example 2: Preparation of pigment dispersions (D-2) to (D-10)]
Instead of B-59 in Example 1, all the pigment dispersions of Example 1 (D) except that B-1, B-20, B-24, B-30, B-54, and B-70 were used. In the same manner as in the preparation of (-1), the pigment dispersions (D-2), (D-3), (D-4), (D-5), (D-6), (D-7) of the present invention. ) Was prepared.
Further, in place of phthalocyanine blue A220 in Example 1, C.I. I. Pigment Red 122 (trade name: CROMOPHTAL Jet Magenta DMQ) manufactured by Ciba Specialty Chemicals, C.I. I. Pigment Yellow 74 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and carbon black (trade name: NIPEX 160-IQ manufactured by DEGUSSA) were all used in the same manner as in the preparation of pigment dispersion (D-1) of Example 1. Pigment dispersions (D-8), (D-9), and (D-10) were prepared.

[Example 3: Preparation of water-based ink for inkjet recording]
Using the pigment dispersion (D-1) obtained above, a pigment dispersion-containing composition having the following composition was prepared, and the composition was centrifuged (at 10,000 to 20,000 rpm for 30 minutes to 2 hours). Water-based ink for ink jet recording (J-1) was obtained.
Pigment dispersion (D-1) 40 parts by mass Glycerol 7 parts by mass Diethylene glycol 9 parts by mass Triethanolamine 1 part by mass Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part by mass Triethylene glycol monobutyl ether 9 parts by mass Ion exchange 34 parts by weight of water When the pH of the ink composition was measured with a pH meter-WM-50EG manufactured by Toa DKK Corporation, the pH was 8.5.
Similarly, inkjet recording inks (J-2) to (J-10) corresponding to the pigment dispersions (D-2) to (D-10) were prepared.

[Comparative Example 1: Preparation of pigment dispersions (D-11) and (D-12)]
B-59 in Example 1 was replaced with copolymer P-30 of Synthesis Example 1 described in [0065] of JP-A-2007-51199, and copolymer S10- of Synthesis Example 8 described in [0071] of the same publication. Pigment dispersions (D-11) and (D-12) were prepared in the same manner as in the preparation of the pigment dispersion (D-1) of Example 1, except that the colorant was changed to 80.

[Comparative Example 2: Preparation of water-based ink for inkjet recording]
In Example 3, ink jet recording inks (J-11) and (J-12) were prepared in the same manner as in Example 3 except that the pigment dispersions (D-11) and (D-12) were used. Prepared.

[Evaluation of pigment dispersion]
(1) Measurement of average particle diameter The volume average particle diameter of the pigment dispersion obtained by the dynamic light scattering method was measured using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). The results are shown in Table 1. Measurement conditions: 10 cc of ion-exchanged water was added to 10 μl of the dispersion to prepare a measurement solution, and measurement was performed at 25 ° C. Evaluation is based on the following criteria.
A: Average particle diameter is 70 nm or more and less than 100 nm ○: Average particle diameter is 100 nm or more and less than 130 nm Δ: Average particle diameter is 130 nm or more and less than 200 nm x: Average particle diameter is 200 nm or more

2. Stability over time of pigment dispersion After the obtained pigment dispersion was left in a sealed state at 60 ° C. for 14 days, the average particle diameter and viscosity were measured for aggregation and thickening of the pigment particles, and the following evaluation criteria were used. evaluated.
(Double-circle): The change of the average particle diameter and viscosity of a pigment particle was not recognized at all.
○: No change in the average particle diameter / viscosity of the pigment particles was observed.
Δ: Slight changes in the average particle diameter and viscosity of the pigment particles were observed, but there was no practical problem.
X: Changes in the average particle diameter and viscosity of the pigment particles were observed, which became a problem in practical use.
The average particle size was measured in the same manner as (1) above, and the viscosity was measured according to the following procedure.
(2) Measurement of viscosity The viscosity of the obtained pigment dispersion was measured at 25 ° C using a TV-22 viscometer (manufactured by Toki Sangyo Co., Ltd.).

[Evaluation of ink for inkjet recording]
1. Evaluation of Printed Product Color Density (Print Density) As an inkjet recording apparatus, a commercially available inkjet recording printer PX-G930 (trade name: manufactured by Seiko Epson Corporation) was used, and inkjet recording inks (J-1) to (J-) were used for this. 12) was filled and printed.
Although any of the inks for ink jet recording of the present invention could be ejected satisfactorily, the ink jetting properties of the comparative ink jet recording inks (J-11) and (J-12) were poor. The results are shown in Table 2.

2. Measurement of average particle diameter The average particle diameter of the obtained ink for inkjet recording was measured by the same method as the measurement of the average particle diameter of the pigment dispersion, and the results are shown in Table 2.
A: Average particle diameter is 70 nm or more and less than 100 nm ○: Average particle diameter is 100 nm or more and less than 130 nm Δ: Average particle diameter is 130 nm or more and less than 200 nm x: Average particle diameter is 200 nm or more

3. Stability over time After the ink for inkjet recording thus obtained was allowed to stand at 60 ° C. for 14 days in a sealed state, the aggregation and thickening of the pigment particles were observed by measuring the average particle diameter and viscosity, and evaluated according to the following evaluation criteria. did.
(Double-circle): The change of the average particle diameter and viscosity of a pigment particle was not recognized at all.
○: No change in the average particle diameter / viscosity of the pigment particles was observed.
Δ: Slight changes in the average particle diameter and viscosity of the pigment particles were observed, but there was no practical problem.
X: Changes in the average particle diameter and viscosity of the pigment particles were observed, which became a problem in practical use.
The average particle size was measured by the method described in 1 above, and the viscosity was measured by the method described in 2 above.

4). Inkjet droplet ejection evaluation The droplet ejection stability was evaluated by visually observing the droplet ejection state. The results are shown in Table 2. Evaluation is based on the following criteria.
◎ ... No discharge failure.
○: There is almost no ejection failure, and there is no practical problem.
Δ: Discharge failure is observed, which is a practically problematic level.
×: Many ejection failures.

As apparent from Tables 1 and 2 above, the pigment dispersion (aqueous colorant dispersion) of the present invention had a fine dispersed particle diameter of the pigment and good stability over time, but the comparative pigment dispersion was It turns out that it is inferior in any evaluation item.
In addition, although the water-based ink of the present invention gave good results in all of the average particle diameter, stability with time, and droplet ejection stability, it can be seen that the comparative water-based ink was inferior in all evaluation items. .

Claims (14)

An aqueous colorant dispersion comprising a colorant (A), a polymer (B), and an aqueous liquid medium (I), wherein the polymer (B) has a hydrophilic structural unit and more than 80% by mass and less than 100% by mass A copolymer containing a hydrophobic structural unit,
The hydrophobic structural unit includes a hydrophobic structural unit (a) containing a benzene ring that is not directly bonded to an atom forming the main chain of the polymer (B),
A structural unit (c) containing a hydrophilic structural unit (b) containing an ionic group as the hydrophilic structural unit and different from the hydrophobic structural unit (a) and the hydrophilic structural unit (b) An aqueous colorant dispersion characterized by containing more than 15% by weight and less than 90% by weight. The aqueous colorant dispersion according to claim 1, wherein the hydrophobic structural unit (a) has a structure represented by the following general formula (1).

(In the formula, * represents a connection point with the main chain, and L represents a divalent linking group having 1 to 30 carbon atoms.) The aqueous colorant dispersion according to claim 1, wherein the hydrophobic structural unit (a) includes a structural unit represented by the following general formula (2).

(Wherein R ₁ represents a hydrogen atom, a methyl group, or a halogen atom, L ₁ represents —COO—, —OCO—, —CONH—, —O—, or a substituted or unsubstituted phenylene group; ₂ represents a single bond or a divalent linking group having 1 to 30 carbon atoms.) The water-based colorant dispersion according to any one of claims 1 to 3, wherein the hydrophobic structural unit (a) includes a structural unit derived from benzyl acrylate or benzyl methacrylate. The aqueous colorant dispersion according to any one of claims 1 to 4, wherein the ionic group of the hydrophilic structural unit (b) is an anionic group. 6. The aqueous colorant dispersion according to claim 1, wherein the anionic group is at least one selected from a carboxyl group, a phosphoric acid group, and a sulfonic acid group. The aqueous colorant dispersion according to any one of claims 1 to 6, comprising a structural unit derived from acrylic acid or methacrylic acid as the hydrophilic structural unit (b). The aqueous colorant dispersion according to any one of claims 1 to 7, wherein the acid value of the polymer (B) is 10 mgKOH / g or more and less than 85 mgKOH / g. The structural unit (c) includes a hydrophobic structural unit derived from an alkyl ester having 1 to 6 carbon atoms of acrylic acid or methacrylic acid, according to any one of claims 1 to 8. The aqueous colorant dispersion described. The aqueous colorant dispersion according to any one of claims 1 to 9, wherein the structural unit (c) includes a hydrophilic structural unit having an alkylene oxide polymer structure. The aqueous colorant dispersion according to any one of claims 1 to 10, wherein the structural unit (c) includes a hydrophilic structural unit having a hydroxyl group. The aqueous colorant dispersion according to any one of claims 1 to 11, wherein the colorant (A) is a pigment. A solution (III) containing a basic substance and containing water as a main component is added to a mixture (II) of a colorant (A), a polymer (B) and an organic solvent (C) capable of dissolving and dispersing the polymer (B). The method for producing an aqueous colorant dispersion according to any one of claims 1 to 12, wherein the organic solvent (C) is removed after the addition. An aqueous ink for ink-jet recording comprising the aqueous colorant dispersion according to any one of claims 1 to 12.